Wiring - Tying into TJ harness (Part 1)

So now we know what each connector
is for and where the wires need to go. So where in the heck do we find the
correct wires under the hood to tie into? That's easy once you've read this!

Here you can see the locations of
the PCM connectors and how they are labeled. Connector 1 has pins labeled Axx,
connector 2 has pins labeled Bxx, and connector 3 has pins labeled Cxx. (We
don't actually tie into any wires that run from connector 2.)

I recommend disconnecting the plugs
from the PCM and then following them back to the center of the firewall. Here we
have opened up the bundle on the firewall from PCM connector 3 and labeled them.
You will only need to identify the brake switch sense wire. (I do not recommend
connecting the CCD bus or SCI transmit wires. Read more on this later in the
article.)

Brake switch
sense - This is a white with pink striped
wire. We need to connect pin 23 on the TCM plug to this wire. Carefully find
the wire and label it. Stu and I stuck a needle into the wire and then checked
it with an ohm meter. Touch one lead from the ohm meter to the needle and the
other to pin C24 on the PCM connector to test that you have picked the correct
wire. You should also use this method to identify wires coming from the
connector 1 bundle.

Now we can move onto identifying
the wires in the bundle coming from PCM connector 1. Once again we need to refer
back to the chart to identify the correct wire color. Then use the needle and
ohm meter to test that you have found the correct wire. Here are the wires that
need to be labeled in this bundle:

Fused Ignition
Switch Output (Start-Run) - This is a dark
blue wire. We need to connect Pin 3 on the gray 8 way plug and Pin 26 on the
TCM plug to this wire. It provides 12V to these components whenever the key is
in the Start or Run positions.

Sensor Ground (Sensor Return) - This is a brown with yellow stripe wire. We
need to connect Pin 16 on the TCM plug to this wire. It completes the sensor
circuits. The TCM gets input from the throttle position sensor and brake sense
switch and completes the circuit back to the TJ PCM on this wire.

Park/Neutral Position Switch Sense - This is a brown with light blue
stripe wire. We need to connect Pin 7 on the gray 8 way connector to this
wire. Whenever the shifter is in the Park or Neutral position this circuit is
completed allowing the starter relay to be engaged by the turning the key.

Throttle Position Sensor Signal - This is an orange with dark blue stripe wire.
We need to connect Pin 17 on the TCM plug to this wire. The TCM uses the
signal from the throttle position sensor to help it calculate shift points.

Ground - There are two ground wires coming from the PCM. They are both black with tan
stripe. We need to connect Pin 24 from the TCM to either one of these.

Now that we have identified all of
the correct wires lets see what it takes to tie it all together!